<?php
/**
 * Helpers collection is used as a registry for loaded helpers and handles loading
 * and constructing helper class objects.
 *
 * CakePHP(tm) : Rapid Development Framework (http://cakephp.org)
 * Copyright (c) Cake Software Foundation, Inc. (http://cakefoundation.org)
 *
 * Licensed under The MIT License
 * For full copyright and license information, please see the LICENSE.txt
 * Redistributions of files must retain the above copyright notice.
 *
 * @copyright     Copyright (c) Cake Software Foundation, Inc. (http://cakefoundation.org)
 * @link          http://cakephp.org CakePHP(tm) Project
 * @package       Cake.View
 * @since         CakePHP(tm) v 2.0
 * @license       MIT License (http://www.opensource.org/licenses/mit-license.php)
 */

App::uses('ObjectCollection', 'Utility');
App::uses('CakeEventListener', 'Event');

/**
 * Helpers collection is used as a registry for loaded helpers and handles loading
 * and constructing helper class objects.
 *
 * @package       Cake.View
 */
class HelperCollection extends ObjectCollection implements CakeEventListener
{

    /**
     * View object to use when making helpers.
     *
     * @var View
     */
    protected $_View;

    /**
     * Constructor
     *
     * @param View $view
     */
    public function __construct(View $view)
    {
        $this->_View = $view;
    }

    /**
     * Tries to lazy load a helper based on its name, if it cannot be found
     * in the application folder, then it tries looking under the current plugin
     * if any
     *
     * @param string $helper The helper name to be loaded
     * @return boolean whether the helper could be loaded or not
     * @throws MissingHelperException When a helper could not be found.
     *    App helpers are searched, and then plugin helpers.
     */
    public function __isset($helper)
    {
        if (parent::__isset($helper)) {
            return true;
        }

        try {
            $this->load($helper);
        } catch (MissingHelperException $exception) {
            if ($this->_View->plugin) {
                $this->load($this->_View->plugin . '.' . $helper);
                return true;
            }
        }

        if (!empty($exception)) {
            throw $exception;
        }

        return true;
    }

    /**
     * Provide public read access to the loaded objects
     *
     * @param string $name Name of property to read
     * @return mixed
     */
    public function __get($name)
    {
        if ($result = parent::__get($name)) {
            return $result;
        }
        if ($this->__isset($name)) {
            return $this->_loaded[$name];
        }
        return null;
    }

    /**
     * Loads/constructs a helper. Will return the instance in the registry if it already exists.
     * By setting `$enable` to false you can disable callbacks for a helper. Alternatively you
     * can set `$settings['enabled'] = false` to disable callbacks. This alias is provided so that when
     * declaring $helpers arrays you can disable callbacks on helpers.
     *
     * You can alias your helper as an existing helper by setting the 'className' key, i.e.,
     * {{{
     * public $helpers = array(
     *   'Html' => array(
     *     'className' => 'AliasedHtml'
     *   );
     * );
     * }}}
     * All calls to the `Html` helper would use `AliasedHtml` instead.
     *
     * @param string $helper Helper name to load
     * @param array $settings Settings for the helper.
     * @return Helper A helper object, Either the existing loaded helper or a new one.
     * @throws MissingHelperException when the helper could not be found
     */
    public function load($helper, $settings = array())
    {
        if (is_array($settings) && isset($settings['className'])) {
            $alias = $helper;
            $helper = $settings['className'];
        }
        list($plugin, $name) = pluginSplit($helper, true);
        if (!isset($alias)) {
            $alias = $name;
        }

        if (isset($this->_loaded[$alias])) {
            return $this->_loaded[$alias];
        }
        $helperClass = $name . 'Helper';
        App::uses($helperClass, $plugin . 'View/Helper');
        if (!class_exists($helperClass)) {
            throw new MissingHelperException(array(
                'class' => $helperClass,
                'plugin' => substr($plugin, 0, -1)
            ));
        }
        $this->_loaded[$alias] = new $helperClass($this->_View, $settings);

        $vars = array('request', 'theme', 'plugin');
        foreach ($vars as $var) {
            $this->_loaded[$alias]->{$var} = $this->_View->{$var};
        }
        $enable = isset($settings['enabled']) ? $settings['enabled'] : true;
        if ($enable) {
            $this->enable($alias);
        }
        return $this->_loaded[$alias];
    }

    /**
     * Returns a list of all events that will fire in the View during it's lifecycle.
     *
     * @return array
     */
    public function implementedEvents()
    {
        return array(
            'View.beforeRenderFile' => 'trigger',
            'View.afterRenderFile' => 'trigger',
            'View.beforeRender' => 'trigger',
            'View.afterRender' => 'trigger',
            'View.beforeLayout' => 'trigger',
            'View.afterLayout' => 'trigger'
        );
    }

    /**
     * Trigger a callback method on every object in the collection.
     * Used to trigger methods on objects in the collection. Will fire the methods in the
     * order they were attached.
     *
     * ### Options
     *
     * - `breakOn` Set to the value or values you want the callback propagation to stop on.
     *    Can either be a scalar value, or an array of values to break on. Defaults to `false`.
     *
     * - `break` Set to true to enabled breaking. When a trigger is broken, the last returned value
     *    will be returned. If used in combination with `collectReturn` the collected results will be returned.
     *    Defaults to `false`.
     *
     * - `collectReturn` Set to true to collect the return of each object into an array.
     *    This array of return values will be returned from the trigger() call. Defaults to `false`.
     *
     * - `modParams` Allows each object the callback gets called on to modify the parameters to the next object.
     *    Setting modParams to an integer value will allow you to modify the parameter with that index.
     *    Any non-null value will modify the parameter index indicated.
     *    Defaults to false.
     *
     *
     * @param string $callback|CakeEvent Method to fire on all the objects. Its assumed all the objects implement
     *   the method you are calling. If an instance of CakeEvent is provided, then then Event name will parsed to
     *   get the callback name. This is done by getting the last word after any dot in the event name
     *   (eg. `Model.afterSave` event will trigger the `afterSave` callback)
     * @param array $params Array of parameters for the triggered callback.
     * @param array $options Array of options.
     * @return mixed Either the last result or all results if collectReturn is on.
     * @throws CakeException when modParams is used with an index that does not exist.
     */
    public function trigger($callback, $params = array(), $options = array())
    {
        if ($callback instanceof CakeEvent) {
            $callback->omitSubject = true;
        }
        return parent::trigger($callback, $params, $options);
    }

}
